At 10:13 AM 3/1/1999 -0500, Tom Rauch wrote:
>I'm not a mechanical engineer, without a tag I don't know which
>way to install a T-shirt, but one thing is obvious.
>Square footage alone is NOT a valid rating.
>Square footage tells us nothing about bending moment moments or
>rotational torque, neither does weight alone....
Amen. Don't failures often occur when the antenna is turning and has just
reached the angle (relative to the wind) where wind pressure and momentum
produce maximum rotating torque, at which point the brake is engaged (on a
non worm-drive rotator). If the torque at that moment exceeds the brake's
ability to hold, then bad things happen to the brake and geartrain.
>From my Yaesu rotator specs, I also notice that the rotating torque is much
less - several times less - than the rated braking torque. To a point, I'd
assume the rotator would simply stall if you try to turn it into too much
wind, but there must be some point where something more destructive
happens, even without the brake engaged.
This is why I'd be interested in seeing a number for maximum wind+momentum
torque (at a specified wind speed) given as part of rotary antenna specs.
73, Pete N4ZR
Loud is good
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